Development of an ultrasound-guided proximomedial approach for injection of the carpal sheath in horses

Introduction

Equine clinicians have embraced  the use of ultrasonography over  the past decade and it  that has been  used routinely as an interventional tool. Several studies have demonstrated the efficacy of the use of ultrasound-guided techniques for different applications within the locomotor apparatus. Intratechal access to  the equine carpal sheath is challenging and without a guaranteed efficacy because is commonly performed  using the ‘blind’ technique. To our knowledge, an ultrasound-guided approach to access the carpal sheath  has yet to be published, so our objective was to develop an easy and reliable ultrasound-guided technique to access the carpal sheath.

Material And Methods

The ultrasound-guided proximo-medial approach technique was firstly developed on 5 cadaver specimens.  10mL of undiluted ionic iodinated contrast medium (Iohexol) was used. Accuracy of the procedure was  verified by contrasted radiographic studies. Afterwards,  the  technique was validated in 5 healthy mature  horses. With the horses bearing weight, the skin was clipped, cleaned, and blocked. Horses were sedated  with xylazine 10% and restrained with a nose twitch. Landmarks for the ultrasound-guided technique were  established and the point of entry was confirmed sonographically. A 21-gauge 1½-inch needle was guided  sonographically between the adius and cephalic vein until the proximal pouch on the carpal sheath was  entered.

Results

Using the ultrasound-guided technique we achieved a 100% accuracy which was confirmed by contrasted  radiographs. No adverse effects were observed during the procedure.

Discussion/Conclusions

Multiples etiologies have been identified to  cause  carpal  sheath  effusion  and  lameness,  nonetheless,  a  reliable and efficient technique to access the carpal sheath for diagnostic and therapeutic purposes needed to be developed. The ultrasound-guided proximo-medial approach for injection of the carpal sheath is  accurate and technically easy to perform. This approach should be considered to access the carpal sheath,  particularly in horses with no evident effusion.

References

1. Tnibar M a. Ultrasound-aided tendon and ligament surgery in the horse. Equine Vet Edu. 2002;14:39–50.
2. Fürr A. Diagnostic Anesthesia. In: Auer J, Stick J, editors. Equine Surgery. 4th ed. St. Louis: Elsevier Saunders; 2012. p.998–1014.
3. Minshall GJ, Wright IM. Tenosynovitis of the carpal sheath of the digital flexor tendons associated with tears of the radial head of the deep digital flexor: Observations in 11 horses. Equine Vet J. 2012;44(1):76–80.
4. Nixon AJ, Schachter BL, Pool RR. Exostoses of the caudal perimeter of the radial physis as a cause of carpal synovial sheath tenosynovitis and lameness in horses: 10 Cases (1999-2003). J Am Vet Med Assoc. 2004;224(2):264–70.
5. Jorgensen JS, Genovese RL, Döpfer D, Stewart MC. Musculoskeletal lesions and lameness in 121 horses with carpal sheath effusion (1999-2010). Veterinary Radiology and Ultrasound. 2015;56(3):307–16.